1. Field of the Invention
The present invention relates to optical pickups and optical disc apparatuses, and is suitably applied to, for example, an optical disc apparatus that records information on an optical disc.
2. Description of the Related Art
Optical disc apparatuses in the related art that are widely available are generally configured to record information on optical discs, such as compact discs (CD), digital versatile discs (DVD), or Blu-ray Discs (registered trademark, referred to as “BD” hereinafter), and to read the information from the optical discs.
An optical disc apparatus uses an objective lens to focus a light beam onto one of helical or concentric tracks formed on a recording layer of an optical disc, and follows the focal point of the light beam.
In this case, in the optical disc apparatus, a light-receiving region provided in a photo-detector optically receives a reflected light beam formed as a result of the light beam being reflected by the optical disc. On the basis of the reception result, the optical disc apparatus calculates a focus error signal and a tracking error signal that indicate an amount of deviation, in a focusing direction and a tracking direction, between the focal point of the light beam and a track at which the focal point of the light beam is to be set. Subsequently, the optical disc apparatus performs focus control and tracking control of the objective lens on the basis of the focus error signal and the tracking error signal.
Some DVD-format or BD-format optical discs are provided with multiple information recording layers so as to have an increased information recording capacity in a single optical disc. An optical disc having multiple recording layers will be referred to as “multilayer optical disc” hereinafter.
In principle, when a light beam is emitted from the optical disc apparatus to this multilayer optical disc, a portion of the light beam is reflected by a recording layer or layers other than a recording layer (referred to as “target recording layer” hereinafter) at which the optical disc apparatus tries to set the focal point of the light beam.
The light beam reflected at the other recording layer or layers is called “other-layer stray light” or “interlayer stray light”. When stray light of this kind reaches the photo-detector, since the stray light is in a defocused state and is incident over a relatively large area on the photo-detector, the incident stray light can sometimes extend to the light-receiving region. In this case, in the optical disc apparatus, since a light reception signal contains an undesired component (stray-light component), the accuracy of the tracking control can possibly be reduced.
In view of this, some optical disc apparatuses are provided with a stray-light-receiving region for detecting the other-layer stray light near the light-receiving region and are configured to correct the light reception signal obtained in the light-receiving region by using a stray-light reception signal in accordance with the amount of light received in the stray-light-receiving region (for example, see Japanese Unexamined Patent Application Publication No. 10-255300 (FIG. 1)).